First of all, the configurations and functions of a conventional keyboard will be illustrated with reference to FIG. 1. FIG. 1 is a schematic top view illustrating the outward appearance of a conventional keyboard. The surface of the conventional keyboard 1 includes plural keys. These keys 10 are classified into several types, e.g. ordinary keys 101, numeric keys 102 and function keys 103. When one or more keys are depressed by a user, a corresponding signal is issued to the computer, and thus the computer executes a function corresponding to the depressed key or keys. For example, when an ordinary key 101 is depressed, a corresponding English letter or symbol is inputted into the computer. When a numeric key 102 is depressed, a corresponding number is inputted into the computer. In addition, the function keys 102 (F1˜F12) can be programmed to cause corresponding application programs to provide certain functions.
With the maturity of computing technologies, the conventional keyboard that has basic functions fails to meet the users' requirements. For this reason, the keyboard manufacturers make efforts in designing novel keyboards with diversified functions. Recently, an illuminated keyboard with an illuminating function has been disclosed. Since the outward appearance of the conventional illuminated keyboard is similar to the outward appearance of the conventional keyboard 1, only the inner structure of the conventional illuminated keyboard will be illustrated in more details as follows. FIG. 2 is a schematic exploded view illustrating a portion of a conventional illuminated keyboard. As shown in FIG. 2, the conventional illuminated keyboard 2 comprises at least one key 20, a metallic base plate 21, a membrane switch circuit module 22, a elastic film 23, an illumination switch circuit module 24 and a main circuit board 25. For clarification and brevity, only one key 20 is shown in the drawing. The key 20 comprises a keycap 201, a scissors-type connecting element 202 and an elastic element 203. From top to bottom, the keycap 201, the scissors-type connecting element 202, the elastic element 203, the elastic film 23, the illumination switch circuit module 24, the membrane switch circuit module 22 and the metallic base plate 21 of the conventional illuminated keyboard 2 are sequentially shown. The main circuit board 25 is disposed beside the membrane switch circuit module 22.
In the key 20, the keycap 201 is exposed outside the top surface of illuminated keyboard 2 to be depressed by a user, the scissors-type connecting element 202 is used for connecting the keycap 201 with the metallic base plate 21, and the elastic element 203 is penetrated through the scissors-type connecting element 202 and contacted with the keycap 201 and the membrane switch circuit module 22. Corresponding to plural keys 20, the membrane switch circuit module 22 comprises plural electrical contacts 221, a first trace pattern 222 and a first bus bar 223. The first trace pattern 222 is connected with the plural electrical contacts 221 and the first bus bar 223. The first bus bar 223 is also connected with the main circuit board 25. When one of the plural electrical contacts 221 is depressed, a corresponding signal is generated and transmitted to the main circuit board 25 through the first trace pattern 222 and the first bus bar 223. In addition, the electricity required for operations of the membrane switch circuit module 22 is also provided through the first trace pattern 222 and the first bus bar 223.
The elastic film 23 is arranged between the elastic element 203 and the membrane switch circuit module 22 for fixing the elastic element 203 thereon. The elastic film 23 comprises a light-shielding layer 231. The elastic element 203 is fixed on the elastic film 23 through an adhesive (not shown). For example, the elastic element 203 is made of a plastic rubbery material. The illumination switch circuit module 24 comprises plural light sources 241, a second trace pattern 242 and a second bus bar 243. The light sources 241 are used for emitting light beams. The second trace pattern 242 is connected with the light sources 241 and the second bus bar 243. The second bus bar 243 is also connected with the main circuit board 25 for receiving electricity. The electricity is transmitted to the light sources 241 through the second bus bar 243 and the second trace pattern 242 to power the light source 241, so that the light sources 241 can emit the light beams.
The internal configurations of the conventional illuminated keyboard 2 are substantially identical to those of the conventional keyboard 1 except that the conventional illuminated keyboard 2 further comprises the illumination switch circuit module 24. For producing the conventional illuminated keyboard 2, the keyboard manufacturer may assemble an additional illumination switch circuit module 24 to the conventional keyboard 1. That is, the conventional keyboard 1 may transmit signals and electricity by connecting the first bus bar 223 with the main circuit board 25. However, the conventional illuminated keyboard 2 is allowed to transmit signals and electricity by connecting the first bus bar 223 and the second bus bar 243 with the main circuit board 25. Due to the additional illumination switch circuit module 24 of the conventional illuminated keyboard 2, the second trace pattern 242 should be connected with the second bus bar 243 while being kept away from the first trace pattern 222. Under this circumstance, since the circuitry layout of the conventional illuminated keyboard 2 is complicated, it is difficult to design the circuitry of the conventional illuminated keyboard 2.